The overall focus of this research isto understand how speech sounds are represented in the brain and how that representation is related to the conscious perception of speech in quiet and in noise. In order to address those questions, an acoustic-phonetic experimental paradigm has been developed. In this approach, behavioral speech perception and neurophysiologic responses to speech signals are measured in the same experimental subject in order to determine relationships between hearing and its neural substrates. Speech-evoked intracranial responses also are measured in an animal model in order to more definitively characterize the auditory system's response to speech signals. Specifically, the relative roles of auditory midbrain, thalamus and cortex as well as left-brain specialization will be examined. In addition to understanding normal speech processing, the project focuses on understanding the pathologies underlying auditory learning disabilities and attention deficit disorders, which are among the most common disorders found in school-aged children. Typically, these children have difficulty perceiving fine-grained speech signals and speech in noise. Another series of experiments will evaluate the neurobiological processes involved in the perceptual learning of speech sounds. The goal is to impact the design of training regimens that may assist these individuals who have difficulty perceiving speech sounds. Overall, the results of this project will further understanding of how speech is represented neutrally and how the normal and impaired auditory systems respond to speech in quiet and in challenging listening environments. Furthermore, the results will delineate the role of neural synchrony in speech perception, and suggest training protocols that may improve speech perception in individuals with impaired hearing mechanisms.